Field of the Invention
The present invention relates generally to a measuring system. In particular, the invention relates to a multi-dimensional laser tracking system for measuring target orientation. More particularly, the systems and methods of this invention relate to a target, or end-effector, for a laser tracking system with a 360° angular working range and capable of precise and large scale point and line surface measurements. The invention further relates to an angular measurement sensor having full 360° angular working range.
Related Art
Precision measuring systems have a wide variety of applications. In robotics, for example, accurate positioning and orientation of a robot is often required. To achieve a high degree of precision, a robot position measuring system can be used. Such a system typically uses a laser beam interferometer to determine the position and/or orientation of a target, or an end-effector, attached to the robot. This system can monitor the position and orientation of the robot end-effector in real-time while providing accuracy, speed and measurement data.
For example, a Three and Five Axis Laser Tracking System is discussed in Applicant's U.S. Pat. No. 4,714,339 and a Five-Axis/Six-Axis Laser Measuring System is discussed in Applicant's U.S. Pat. No. 6,049,377, both of which are incorporated herein by reference in their entirety. Additionally, a Multi-Dimensional Measuring System is discussed in Applicant's U.S. Pat. No. 7,230,689 and U.S. application Ser. No. 11/761,147 and Ser. No. 11/870,666, which are also incorporated herein by reference in their entirety to provide additional description for the present invention. An Accurate Target Orientation Measuring System is discussed in Applicant's U.S. Pat. No. 7,400,416, which also is incorporated herein by reference in its entirety.
Touch-type probes and optical scanners are two types of sensors commonly used with the target, or end-effector, of a laser tracking system to obtain measurements of an object or surface of interest. Probes provide measurement of a point or multiple points with a high level of accuracy while scanners provide for rapid measurement of multiple points. Each type of sensor provides advantages dependent upon its application.
In U.S. Pat. No. 7,230,689, Applicant describes a probe assembly affixed to an active target for a laser tracking system which provides for measurement of a point which is not in the line-of-sight of the tracking unit, or, alternatively, the point to be measured is inaccessible by the target. The disclosed device permits, for example, the rapid measurement of deep recesses and hidden points on large structures and parts with high accuracy. Using interchangeable probes, an operator can change probe size, probe angle or probe orientation at any time to better access a measured surface. Measurements of hidden points, detailed features and deep recesses can be obtained which cannot be measured with traditional laser tracker tools.
The touch probe assembly described in Applicant's aforesaid patent, as well as other probes of known design, have an angular working range which is limited by the acceptance angle of the retro-reflector on the target. This working range generally is ±35° in pitch, yaw and roll. For extended working range, the probe has to be re-configured, generally with another probe having a different configuration, and re-calibrated each time. With other probes of known design, the target and probe have to be re-oriented and re-calibrated before additional measurements can be made.
There are many situations which require the accuracy and measuring capability provided by a point-type probing device and the speed provided by a scanning measurement device. Up to now, a separate measurement device was required to use each type of sensor. A capability of quickly changing from a probing device to a scanning device would increase the accuracy of the measurements and greatly enhance the speed with which measurements are made. These advantageous features could further be enhanced if the angular working range of the measurement device could be extended beyond the customary ±35° limit without the requirement of re-configuring and re-calibrating the device.